Definition and scope of antibiotics

Summary

An antibiotic is an antimicrobial substance that is active against bacteria and is a key antibacterial agent used to treat and prevent bacterial infections. Antibiotics may either kill bacteria or inhibit their growth. In medical usage, “antibiotics” most commonly refers to drugs that are produced naturally by microorganisms (for example, penicillin), whereas other antibacterials such as sulfonamides and antiseptics are fully synthetic; both categories can prevent or kill microbes, but antibiotics are a specific class within antimicrobial chemotherapy. The scope of antibiotics includes their use in medicine for bacterial infections and, in some cases, certain protozoal infections (e.g., metronidazole). They are used therapeutically when a pathogen is suspected but not yet identified (empiric broad-spectrum therapy) and when the causative organism is known (definitive therapy, often with narrow-spectrum antibiotics). Antibiotics are also used preventively in at-risk populations (such as people with weakened immune systems), in surgical prophylaxis to reduce incision infections, and in dental prophylaxis to help prevent bacteremia and infective endocarditis. They can be administered orally in most cases, intravenously or by injection for severe systemic infections, and topically (e.g., eye or ear drops) when the infection site is accessible.

Key Points

• 1

  Antibiotics are antibacterial antimicrobials that either kill bacteria or inhibit their growth, and they are central to treating and preventing bacterial infections.

• 2

  In usual medical usage, antibiotics are typically naturally produced by microorganisms, while other antibacterials (e.g., sulfonamides, antiseptics) may be synthetic, though both can act against microbes.

• 3

  Antibiotics are used both therapeutically (empiric broad-spectrum or definitive narrow-spectrum) and preventively (e.g., surgical, dental, and immunocompromised patients).

• 4

  They are administered via multiple routes—most commonly orally, but also intravenously/injection for severe infections and topically for accessible localized infections.